Commentators had warned that Mr Le Pen could put the incumbent president on the spot over the string of allegations concerning sleaze and corruption when he was mayor of Paris, as well as raising other awkward issues.

But Mr Chirac insisted that his decision was a principled one.

Jean-Marie Le Pen

Born in 1928 in the Brittany town of La Trinite-sur-Mer

Set up the National Front in 1972

In 1987 he described the Holocaust as a "detail of history"

Wants 200,000 new prison places, the abolition of inheritance tax and a renegotiation of European treaties

"Just as I did not accept any alliance in the past with the National Front, whatever the political price, I will not accept a debate with its leader in the future," he told a campaign rally in the western city of Rennes.

"You must have the courage of your convictions and the steadfastness of your commitments."

A student confederation called a mass protest to coincide with Mr Le Pen's television appearance on Tuesday evening, at the end of a day of demonstrations against his shock election success.